Our invention relates generally to apparatus for data transfer with a recording disk, such as a flexible magnetic disk, that is housed in an apertured protective envelope to make up a disk cartridge, and particularly to improved means in such apparatus, generally referred to as a disk drive, for centering and clamping the recording disk in position preparatory to data transfer with a transducer head assembly or a pair of such assemblies.
Mathurin U.S. Pat. No. 3,768,815 and Rolph U.S. Pat. No. 4,125,883 represent typical conventional examples of means for centering and clamping a flexible magnetic disk in a disk drive. These and other comparable prior art devices commonly employ a tapered, flanged collet rotatably mounted to a hinged clamp carrier, such as a cover forming a part of the housing of the disk drive or a clamp arm mounted within the housing, for movement into and out of engagement with a socketed drive hub via the central hole in the magnetic disk. As is well known, the magnetic disk is somewhat loosely housed in an apertured, generally square protective envelope. Consequently, even though the disk cartridge itself may be correctly positioned with respect to the drive hub, the magnetic disk therein may be displaced or have play, in its own plane within the envelope and so may be out of axial alignment with the drive hub. This will present no serious problem with disk drives of usual thicknesses, or dimensions in the axial direction of the drive hub, as the tapered collet will, in most cases, nevertheless pass through the central hole in the magnetic disk for centering same.
The current trend with disk drives, however, is toward the reduction of their thicknesses. This requires the minimization of the axial dimensions of both drive hub and collet. The tapered collet of such reduced axial dimension may fail to center the magnetic disk if it is displaced too much within the envelope, thrusting the edge of the disk around its central hole into the socket in the drive hub and so ruining the disk. The possibility of the collet ruining the magnetic disk becomes even higher as the collet is usually mounted to a hinged carrier as aforesaid and so must follow an arcuate path in traveling into engagement with the drive hub.